Head pressure -- how much flow am I really getting

[125mph]

I'm running a 57W UV so I'm trying to dial in the flow. The UV is plumbed directly into the return.

I have so many elbows and T's and an unused manifold, I think its too inaccurate to calcuate the head pressure. Here's a video of my return flow.. Do you think this is around 300gph, 500 or 800? Guestimate?

The return is split into two nozzles.

 

[125mph]

 

[FUNGI]

Pump Turnover Calculator

Aquarium calculator; Estimate the time required for a pump to process a specified percentage of an aquarium system's water.

www.hamzasreef.com

 

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https://www.freecalc.com/fricfram.htm